Back door leaking - what could be the cause?

neilmcl

It's a wedge gasket that's shrunk over time, completely normal and very easy and cheap to fix. Just lift out a bit of the gasket to check what style and the width of it then order some online, you can get in various places for around a £1 per metre. If you're unsure what type it is then order some sample packs so you can eventually order the correct size.

https://www.windowrepairshop.co.uk/Gaskets/Wedge-Gasket

You don't any special tools to fit, just something that you can use to lift the old ones out without splitting them, the new ones will simply push back in.